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Drive side oil seal .

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Drive side oil seal .

Postby neil64 » Sat Jul 27, 2019 8:33 am

Hello.

Seem to have quite a bit of smoke coming from scooter when running ,how do you check the drive side seal is good ?
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Re: Drive side oil seal .

Postby MickYork » Sat Jul 27, 2019 9:05 am

Check your oil level. If your losing oil and unless there's a visible leak the oil seal would be a good bet.

A leak test would be the next step.......
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Re: Drive side oil seal .

Postby ULC Soulagent » Sat Jul 27, 2019 12:59 pm

Put ur hand ( protected) over the end of the exhaust tailpipe and providing u don’t have any leaky joints then if ur seal has gone then the engine will still run :?
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Re: Drive side oil seal .

Postby Scooterlam » Mon Aug 12, 2019 8:37 pm

ULC Soulagent wrote:Put ur hand ( protected) over the end of the exhaust tailpipe and providing u don’t have any leaky joints then if ur seal has gone then the engine will still run :?

Heard this many times.
Can anyone explain this
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Re: Drive side oil seal .

Postby Tractorman » Mon Aug 12, 2019 9:14 pm

If the exhaust gases cannot get out the inlet gasses cannot enter. Ramming a potato up a car exhaust was a popular trick!
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Re: Drive side oil seal .

Postby Scooterlam » Mon Aug 12, 2019 10:03 pm

So what were led to believe is if the DS oilseals gone and the pipe is blocked. At bdc the exhaust gas is exiting via the opposite transfer into th pc chamber without mixing withor igniting the new charge and out thru DS oil seal whilst simitaniuosly fresh charge iis drawn thru the remaining transfer?
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Re: Drive side oil seal .

Postby Warkton Tornado No.1 » Mon Aug 12, 2019 10:49 pm

Scooterlam wrote:So what were led to believe is if the DS oilseals gone and the pipe is blocked. At bdc the exhaust gas is exiting via the opposite transfer into th pc chamber without mixing withor igniting the new charge and out thru DS oil seal whilst simitaniuosly fresh charge iis drawn thru the remaining transfer?


It's nothing to do with the exhaust pipe being blocked.

It's all to do with the pumping process of the bottom end. If a crankshaft oil seal fails, particuarly on the drive side, then the primary compression chamber will effectively 'communicate' with the chaincase & suck in oil & air from it in exchange for exhaust products when it is not sucking, but blowing. To sum up, when the engine should be pushing spent fuel gases only out of the exhaust, some will get blasted into the chaincase.

If a drive side oil seal is doing it's job, as quite rightly mentioned, a hand over the tailpipe should cause the engine to falter, or stop.

(I've long since concluded that primary compression, or the raising of it, is not something worth pursuing, particuarly when the engine is being run with good expansion chambers in conjunction with other tuning measures to raise power. I have known people run engines for thousands of miles with a blowing drive side oil seal & they just kept topping up the chaincase until a time of convenience in which to change it.... ;) )
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Re: Drive side oil seal .

Postby Scooterlam » Mon Aug 12, 2019 11:44 pm

Wt1

We must really meet up over a pint and bore the pants off everyone around us. :D
I'm trying to put all the pieces together.
And I'm having trouble with a weeping seal allowing a cylinder to purge a cylinder of enough gas to not allowing ghosting to occur. Or in the case of piston porting the air flow in the ventura stalling as the piston skirt opens the inlet
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Re: Drive side oil seal .

Postby Scooterlam » Tue Aug 13, 2019 12:32 am

Wt1

We must really meet up over a pint and bore the pants off everyone around us. :D
I'm trying to put all the pieces together.
And I'm having trouble with a weeping seal allowing a cylinder to purge enough gas to not allowing ghosting to occur. Or in the case of piston porting the air flow in the ventura stalling as the piston skirt opens the inlet

BTW thanks for your explanation and hopefully patience
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Re: Drive side oil seal .

Postby Fast n Furious » Tue Aug 13, 2019 12:49 am

neil64 wrote:Hello.

Seem to have quite a bit of smoke coming from scooter when running ,how do you check the drive side seal is good ?

Warm your engine up and leave it ticking over.
Place a piece of cling film over the breather plug and secure with a tight elastic band. ( you can also use a balloon but this is not usually a part of the wife's tool kit!) :lol:
If it tries to suck the clingy down the breather hole then this is indicative that the chaincase is pulling a vacuum when it should be producing a slight pressure.
If it pulls a vacuum or pulses with each rev, chances are your DS seal or DS bearing is knackered.
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